Automatic analysis devices are used for tests in various different fields, such as for an immunological test, a biochemical test, or a blood transfusion test to analyze many samples. Automatic analysis devices quickly and highly accurately analyze an intended substance among many components contained in each sample.
Automatic analysis devices include an immune analysis device that quantitatively or qualitatively detects, through immunoreaction, an intended substance (such as antigen or antibody) contained in a sample (such as serum, blood plasma, or urine). An immune analysis device includes a system for bound-free (BF) separation performed to separate an intended substance in the sample, which is to be analyzed, from a reaction solution and wash the intended substance using a reagent in which an antigen or an antibody that reacts on the intended substance in the sample is combined with a solid phase (such as a magnetic particle).
For BF separation, a nozzle of an automatic analysis device that uses magnetic particles is inserted into a reaction solution in a reaction vessel and caused to suck the reaction solution in the reaction vessel. At this time, the reaction solution is sucked while the magnetic particles are temporarily attracted to (magnetically collected on) an inner wall surface of the reaction vessel by magnets disposed outside the reaction vessel so that the magnetic particles that form immune complexes contained in the reaction solution are not sucked. Thus, only magnetic particles that are bound to an intended substance to form immune complexes are left in the reaction vessel and other unreacted sample-derived components or the like are removed through the sucked solution. Thereafter, a washing liquid is discharged and sucked through the nozzle to and from the reaction vessel, so that the magnetic particles in the reaction vessel are washed. The number of times the BF separation operation is performed is determined depending on the conditions of an analysis of an intended substance.
Various different types of BF separation mechanism for an automatic analysis device have been developed to efficiently perform the BF separation. A disclosed example of a device performs two steps of magnetic collection on a reaction vessel using one magnet disposed on one side surface of the reaction vessel (see, for example, PTL 1). In addition, a disclosed example of a device that is equipped with a BF separation mechanism performs two steps of magnetic collection using first magnetic means and second magnetic means before performing BF separation (see, for example, PTL 2).